The present invention is related to a voltage regulator for a computer processor having different voltage settings. More particularly, the present invention is related to a voltage regulator for a computer processor where the voltage setting may be changed if the processor is at a cold temperature.
In processor chips for computers and other electronic equipment, the amount of power used is an important factor which needs to be controlled. In some environments, power is provided by a battery or other limited power source so that the use of small amounts of power is desirable. For many types of devices, the amount of power determines the amount of heat generated, which must be dissipated in order for the device to work properly. For these and a number of other reasons, it is important that the amount of power utilized be kept small. It is also important to keep the variation in the power dissipation as small as possible, so that the power supplied is somewhat constant.
The power utilized for a switching element can be divided into a leakage part and a dynamic part. The leakage part exists even if the component stops executing any new instruction or if the processor is doing nothing. The dynamic part is the part which is actually utilized when the processor and element are active. The active portion is often about 60-70% of the total amount of power utilized . This active portion is proportional to the square of the voltage, based on the basic formula of power equals the square of the voltage divided by the resistance. However, because this power is used only when the switching is active, the power is also proportional to the frequency of switching. This relates to the amount of time that the switching element is active. Since the power is proportional to the square of the voltage, it is important that the supply voltage be kept as constant as possible. Any changes in the supply voltage will produce even larger changes in the power function.
Unfortunately, many electronic elements and especially switching devices such as CMOS devices have a temperature dependency. For a given temperature range, the switching frequency capability of the device depends on the supply voltage. Likewise, the ability to turn on and off the device depends on the supply voltage. Similarly, for a given supply voltage the switching frequency capability of the device depends on the temperature. It should especially be noted that if the device is cold it may not work at all, especially if the applied voltage is low. Other variables such as interconnecting power delivery issues may also depend on the temperature.
Thus, it is important that the supply voltage for a processor having CMOS devices remain within appropriate limits for the temperature range it was designed. One example is that a processor, such as the LV-Pentium-III(trademark), running at 300 MHz has a desirable supply voltage of 0.975Vxc2x125 mV at a temperature of 15xc2x0 C.
However, if the device is colder than this it is necessary to increase the supply voltage in order to keep the device running at 300 MHz. This compensation is on the order of 1 mV/xc2x0 C. For example, if the supply voltage is nominally 0.975V at 15xc2x0 C., and the processor is actually at 0xc2x0 C., the supply voltage must be raised to 0.990V. Thus, a 15 mV adjustment is added due to the temperature variation. This increase of 15 mV will increase the processor core power dissipation by about 3%. If the supply voltage is not increased, many of the processors will not operate properly and accordingly will not pass the required standard tests. However, if the supply voltage is adjusted to be higher when the temperature is cold, many more of the processors will pass the test and be usable. Thus, it is desirable to have a supply voltage which changes depending on the temperature of the processor so that the percentage of manufactured processors which pass the tests is as high as possible.